Media Blog- PGD/PGS
CHR Blog: Other examples of misguided policies
Unfortunately, PGS is not the only IVF practice, introduced with good intentions but negative patient results. The idea of introducing changes to established IVF practice patterns, based on theoretical concepts but without appropriate statistical support, has in recent years resulted in dramatic changes to routine IVF. Its most far-reaching consequence is probably the concept of single embryo transfer (s-ET).
Starting in Scandinavia, s-ET has in recent years conquered Europe and is starting to make inroads into the U.S. The concept is based on data, which demonstrate that risks and costs of twin pregnancies are greater than those of singletons. As a consequence, proponents of s-ET argue that twin pregnancies are to be avoided; - hence, the concept of s-ET since it, indeed, will avoid most twin pregnancies.
Unfortunately, the concept is, once again, based on categorically wrong statistical considerations. Like with PGS, CHR’s Drs Gleicher and Barad pointed out this fact in a recently published paper in the ASRM journal Fertility and Sterility (Gleicher and Barad, Fertil Steril 2009;91:2426-2431): While there can be no doubt that twin pregnancies carry higher outcome risks and, therefore, costs than singletons, this comparison from the obstetrical literature is based on a retrospective obstetrical paradigm, where comparisons are made post-factum about a previously established pregnancy, with reference point pregnancy.
In contrast, an infertility-based paradigm is prospective, and the appropriate reference point for outcome is birth of a child. A vast majority of patients, entering fertility treatment, are desirous of more than one child. A couple wanting two children, therefore, has two choices: they can achieve their goal via one twin or two singleton pregnancies. In this kind of a treatment paradigm, in contrast to the previously noted obstetrical paradigm, the statistically correct comparison is, therefore, not between one twin and one singleton pregnancy but between one twin and two singleton pregnancies.
When this is done, as Gleicher and Barad reported in the above noted paper, twins no longer demonstrate relevant increased risks and/or costs. The authors, therefore, concluded that, in contrast to prevailing opinion, twin pregnancies, except in exceptional situation, represent a favorable outcome in infertility.
It is undisputed that s-ET reduces pregnancy rates in comparison to the transfer of two embryos. Since the whole concept of s-ET is based on avoiding excessive risks and costs from twin pregnancies, the only logical remaining conclusion is that the concept of s-ET, for a vast majority of women, simply does not make sense. s-ET reduces pregnancy chances at no compensatory benefit to the patient and should, therefore, be considered contraindicated, unless patients are in infertility treatment with the specific desire of having only one child or if obstetrical contraindications exist towards delivery of twins.
In widely propagating the concept of s-ET, professional organizations are, once again, on the wrong side of medical history. It will be interesting to see how long it will take in this case until they come around in their formal opinions.
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CHR's Media Blog is a compilation of potential story ideas gathered from infertility-related news, our research, and our opinion to facilitate open communication with the public on this increasingly relevant field of medicine.
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